Body weight and the energetics of temperature regulation.

The recent rebirth of interest in the 200-year-old field of homoiothermic energetics may be dated from three papers published in 1950 by Scholander, Irving and colleagues. These papers furnished many data and a theoretical analysis of the energetics of temperature regulation in tropical and arctic birds and mammals. A massive body of data has since become available through the efforts of many workers. Unfortunately, there has been little effort to extend Scholander and Irving's model (which was based on Newton's law of cooling) to meet the challenge of new data. One of the peculiarities of this model is that it is presented in a weight-independent form, although two of its parameters, basal rate of metabolism and thermal conductance, are well-known to be weight-dependent. In this paper the influence of weight on the energetics of homoiotherms will be re-examined; special attention will be given to the applicability of Newton's law of cooling.